[Imported] DNP3 "Start MDRP Comms" alarm

[sbeadle]

>>Message imported from previous forum - Category:ClearSCADA Software<<
User: florian, originally posted: 2018-10-25 17:15:34 Id:250
This is a re-posting from the obsoleted (October 2018) "Schneider Electric Telemetry & SCADA" forum.

-------------------------------

**_hardin4019:_**
**_Having issues with some DNP3 outstations over a satellite link. The connection drops to a site. The Comms Failed alarm raises, then 3 minutes later "Scanner command (Start MDRP Comms) Timed Out - Alarm Raised", then less than a minute later comms are re-established and the initial comms alarm clears. But there is a redirection setup to run after 59 minutes and the "Start MDRP Comms" alarm never cleared. Is there an explenation of what MDRP is or how to shut it off? I couldn't find anything in the help file._**

-----------------------

bevanweiss:
The 'Scanner command (Start MDRP Comms) Timed Out' I believe is normally an 'on server' error.. meaning that ClearSCADA didn't get a response back from the DNP3 driver for the Start MDRP Comms request within a suitable period of time (like 30seconds I think).
https://www.schneider-electric.com/en/faqs/FA336677/

Are the TCP settings of the server modified from the standard Windows settings (like the TCP timeout is set significantly higher or such?)

My recommendations from previous experience with satellite link is to use UDP instead of TCP. The handshaking of TCP is killer with the latency of satellite links.
If you use UDP and you have previously turned off Data Link Layer acknowledgement in the DNP3, then you probably want to turn this back on however (since with UDP you don't get the 'reliable comms channel' that TCP provides).

------------------

**_hardin4019:_**
**_Thanks for pointing me in the right direction Bevan. I'll give this a try._**